Drawing apparatus

ABSTRACT

This invention has to do with drawing apparatus and, more particularly, to a drawing board and a straightedge having interengaging parts to permit their operation in drafting.

United States Patent Inventors Walter Hebel; [56] References Cited Ulrich Hebel. both of Heleneweg 7, 5242 UNITED STATES PATENTS Kirdier, Germany pp NO' 777,363 2,219,766 10/1940 Cotterman Filed Nov. 20, 1968 FOREIGN PATENTS Patented June 29. 1971 456,291 2/1928 Germany Priority Nov. 20, 1967 453,405 9/1936 Great Britain....

Germany 597,020 1/1948 Great Britain B60876 671,486 5/1952 Great Britain Primary Examiner-Harry N. Haroian DRAWING APPARATUS Attorney-Norman S. Bl0dgii 17 Claims, 33 Drawing Figs.

US. Cl 33/76 Int. Cl B431 13/02, ABSTRACT: This invention has to do with drawing apparatus B431 7/02 and, more particularly, to a drawing board and a straightedge Field of Search 33/76, 79, having interengaging parts to permit their operation in draft- 80 ing.

2 I: 14 I E 11 i mi 3 12 l 8a i XIX PATENFEUJUNZSIBYI 3.589.016

sum 1 OF 5 INVENTORS ULRICH HEBEL WALTER HEBEL PATENTED-JUNZQIBYI 3,589,016

SHEET s 0F 5 8 4 W IIIIIIIIIl/I/II/o VIIII/IIIIIIII/III 1o 4 I///IIIIIl/IIIIIIIIII III/II/III/IIIIII/ PATENTEDJUNZSIBYI 3,5 9,016

SHEET 5 OF 5 501. 2 I 1 I IIIIIIIIIIIII Elgjs b DRAWING APPARATUS BACKGROUND OF THE INVENTION Many attempts have been made in the past to develop a portable drafting board and straightedge. For instance, the German Pat. Nos. 1,873,930 and 1,972,827 Sl'lOW drafting devices of the above-mentioned type. On the drafting device according to the first-named patent, a guide groove for the straightedge is arranged within a clamping bar, which acts to lock drawing paper in place, the bar being positioned underneath the drawing plane in recessed position. This guide groove is directed with a support edge, to the drawing plane of the plate, pressed against a straightedge with a guide piece, also having a rectangular edge directed to the drawing plane. The arrangement of the guide edges on the clamping bar and on the guide piece of the straightedge is such that, for the exact guidance of the straightedge, the straightedge has to be pressed down on the drawing plane. This has the disadvantage that the forces are released in the same direction as the forces used for the drawing of horizontal lines. The result is an insecure drafting procedure because the drawing apparatus may slip in the direction of the forces and this may result in an unclean drawing. On the drawing apparatus according to the German Pat. No. 1,972,827, these disadvantages are eliminated because the guide groove within the plate and also the guide piece on the straightedge have a trapezoidal cross section, so that the guide piece needs only to be pressed into the guide grooves from above to achieve an exact guidance. The holding forces for the straightedge, therefore, may be applied with the left hand away from the drawing plane, that is, to the left side, so that the forces, created by horizontal drawing of lines, are directed to the right and therefore opposite. A secure support for the straightedge and, therefore, secure operation are guaranteed.

However, there still is a disadvantage in the drawing apparatus shown in the German Pat. Nos. 1,873,930 and 1,972,827; that is, that with the straightedge, an accurate measuring of distance on any chosen place on the drawing plane is not possible. The disadvantage results from the guide pieces extending a considerable distance over the underside of the straightedge. Therefore, a complete tight fit of the measuring edge of the straightedge to the drawing area is only guaranteed as long as the guide piece is engaged with the guide groove of the. drawing plate. However, when the straightedge is put down on the drawing in such a way that its guide. piece also rests on the drawing surface, then there is (at least on the end of the straightedge where the guide piece is positioned) a con.- siderable space between the measuring edge and the drawing plate. This prevents the exact measuring of distances.

The same disadvantages are present with the drawing devices described in the German Pat. No. 1,758,026, in the French Pat. No. 1,103,267, in the U.S. Pat. Nos. 2,807,090; 3,101,568; 2,908,079, in the German design Pat. Nos. 1,840,318; 1,748,928; 1,847,742;and 1,962,815.

The German Pat. No. 804,647 shows a drawing apparatus in which the guide groove on the drawing plateand the guide piece on the straightedge have a trapezoidal-shaped cross section, so that an exact guiding of the straightedge may be achieved by application of holding forces directed away from the drawing area. In this case however, the guide groove is positioned considerably above the drawing plane in an added strip, where the clamping bar is also located for clampingthe drawing sheet. Such a design of drawing apparatus permits the accurate measuring of distances at a desired part of the drawing area with the help of the straightedge, because, the straightedge is equipped with an offset for the purpose of cn-. gaging the guide groove. The disadvantage, however, is that the strip extends over the drawing area and does not permit working close to the edge during drafting or when using templates or French curves.

A drawing apparatus, which does not have these disadvantages and by which can be achieved an accurate guiding of the straightedge by holding forces opposed to the forces created by working, is made known through the German Pat. No. 1,962,815. In this known drawing apparatus, a guide groove of rectangular shape is worked. into the drawing board and the guide piece on the straightedge is of trapezoid-shaped cross section. The trapezoid-shaped cross section of the guide piece is limited on the edge close to the side by an area vertical to the drawing plane, and the edge of the guide piece away from the side of the plate is limited toward the top running sloped to the drawing plane. This drawing apparatus, however, as on all previously described known drafting devices, the disadvantage still exists that the guide piece for the straightedge (for the execution of the different consecutive working operations, namely the drawing of horizontal and vertical lines and the measuring ofdistances on the different places on the drawing plane) has to be lifted every time by hand toward the top from the guide groove of the board, A continuous performance of the three main functions of drafting, namely the consistent measuring ofdistances in addition to the drawing of vertical and horizontal lines, is strongly influenced by such interruptions.

All these functions however, can be: performed adequately with the drawing apparatus shown in the German Pat. No. 960,880; however, the disadvantage appears again that work close to the sides of the drawing board and also work close to the drawing board with templates and French curves, cannot be made, because of the two guide strips which are arranged together at a right angle and extend above the drawing area. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a drawing apparatus which eliminates the disadvantages of the prior art and brings together all the advantages.

Another object of this invention is the provision of a drawing apparatus in which all the operative elements are located under the drawing plane.

A further object of the present invention is the provision of a drawing apparatus in which the guide grooves in the board and also the guide piece on the straightedge, have such a design, that the straightedge, for fast operation of the three main drafting functions may be engaged or disengaged from the guide grooves of the plate simply by sidewise displacement.

It is another object of the instant invention to provide the arrangement of the guide piece on the straightedge is such that its measuring edge in any case, even at its zero point, lies tightly against the drawing area, which makes it possible to measure distances accurately and exactly on any place of the drawing area.

SUMMARY OF THE INVENTION In general the present invention consists of a drawing apparatus having a board as carrier for the drawing sheet and a straightedge movable on this plate. The straightedge is movable parallel to and in exact alignment with a guide piece which is positioned in a right angle to its working edge. The guide piece is connected to guide grooves formed in the surface of the board and arranged parallel to the outer edges. A clamping bar is arranged underneath the drawing plane of the plate and recessed for locking the drawing sheet to the plate in working position.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated bythe accompanying drawings, in which:

FIG. 1 is a plan view of a drawing apparatus embodying the principles of the invention,

FIG. 2 is a vertical sectional view of the invention taken on -.he line II-II of FIG. 1,

FIGS. 30, 3b, and 3c are plan, side elevation, and front elevational views, respectively, of a straightedge forming part of the apparatus,

FIGS. 4a, 4b, and 4c are plan, side elevational, and front elevational views, respectively, of a modified form of the straightedge,

FIGS. 5a, 5b, and 5c are plan, side elcvational, and front elevational views, respectively, of another modification of the straightedge,

FIGS. 6a, 6b, and 6c are plan, side elevational, and front elevational views, respectively, of a still further modification of the straightedge,

FIGS. 7a, 7b, and 7c are plan, side elevational, and front elevational views, respectively, of another modified form of the straightedge,

FIGS. 80 and 8b are plan and side elevational views of a modification of the straightedge,

FIGS. 9a and 9b are sectional and plan views of another form of the invention,

FIGS. 10, ll,l2,13,14, l5,16a,16b, l7,and 18 show various forms of interengagement between the straightedge and the board,

FIG. 19 is a sectional view of the apparatus taken on the line XIX-XIX of FIG. I, and

FIG. 20 is a sectional view of the apparatus through the left side of the board with a movable scale within the guide groove.

DESCRIPTION OF THE PREFERRED EMBODIMENT According to this invention, the guide grooves in the board and the guide piece on the straightedge are formed with cross sections of trapezoid shape; the outer areas of the grooves and guide piece, i.e., those close to the edge of the board, are made vertical to the plane of the board. The guide areas for the grooves and the guide piece slope upwardly toward the drawing area. The arrangement, wherein the guide areas for grooves and guide piece directed vertically to the drawing area and close to the plate edges, guarantees an accurate guidance of the straightedge by causing the holding forces to be mainly directed away from the drawing plane, that is, directed in opposition to the working forces created by the drawing of horizontal and vertical lines. The design of the grooves and guide pieces with the sloped surfaces located toward the center of the drawing plane, guarantees a hindrance-free engagement and disengagement of the guide piece with the guide grooves during necessary exchange of drawing functions by simple parallel displacement of the straightedge on the drawing plane. A lifting of the straightedge for disengaging its guide piece from the guide groove of the board is not necessary.

According to this invention, it was found very useful to arrange guide grooves, for engaging of the guide piece of the straightedge, on all four sides of the plate. The invention suggests furthermore that the guide grooves run out on one of their ends with a certain distance from the plate edge. By this method the stability of the plate will be considerably increased in comparison to the prior art arrangements wherein such guide grooves are running all the way through the to the edge.

A further task of this invention is to create a tight fit of the measuring edge of the straightedge to drawing surface for measuring distances accurately on any desired place on the drawing area. This is accomplished by constructing the apparatus so that the guide piece ends a substantial distance from the measuring edge. According to this invention, this is made possible by providing that the guide piece of the straightedge increases in thickness (in the shape of a wedge) starting at the working edge.

Another solution to the task of this invention is, to form the guide piece partially with constant thickness but to form it a suitable distance from the measuring edge with a tilt edge, in

such a way that the guide piece slopes towards the measuring edge. The wedge-shaped design of the guide piece guarantees a tight fit of the measuring edge of the straightedge over its total length for measuring of distances on the drawing area, with the design of the guide piece of constant thickness up to a tilt edge, however, it is necessary for accurate measuring of distances to create a tight fit for the measuring edge, with its total length over the drawing area, by pressing the finger lightly on the measuring edge in the vicinity ofthe guide piece.

The same effect may also be achieved when the straightedge as guide piece is formed as two separated portions, of which one is placed in a sufficient distance from the measuring edge of the straightedge and, therefore, a tilt edge can be formed. It is also possible to design the guide piece with a corrugated strip at least on one side of the straightedge. The guide piece also may be designed by beveling of one edge of the straightedge.

It is also of advantage to provide guide pieces on both the top and bottom of the straightedge. They may be identical in shape, but also may differ from each other. This characteristic makes it possible to use the straightedge turned around This is useful especially when the side lines around the drawing sheets are to be made or when the edge opposite from the measuring edge of the straightedge is positioned in a certain angle for example 75, for lettering. According to this invention, the underside of the guide piece close to the side may be beveled or rounded for the purpose of slipping more easily over the guide grooves and the plate clamping bar during measuring or swinging of the straightedge. To simplify the use of the guide edge interchangeably for drawing horizontal and vertical lines, there is within the griphole of the straightedge arranged, a turning piece in the shape of a button, or ring, or socket which has radial grooves for easy swinging of the straightedge. Also it is suggested to build a magnet into the turning piece, which keeps the straightedge automatically straight in the frequently used guide groove of the plate; this is true when the clamping bar is made from material which is attracted to a magnet.

To make a drawing apparatus with the maximum stability and the least weight, the recess in the board is limited by barriers, even on the side away from the drawing area; the top of these barriers is of the same height as the drawing plane. The recess for the plate-clamping bar is formed with several recesses on the barrier side away from the drawing area. The pressing of the plate-clamping bar by the fingertips is, therefore, much easier.

The plate-clamping bar is equipped, approximately in the center of its cross section, with a U-shaped impression or a double beveling which acts, when pressed down, as a tilt edge for the plate-clamping bar and as a stop for the inserted drafting paper.

On the base of the recess for the clamping bar is formed a ridge on which the tilt edge of the clamping bar is supported by pressing down. This design lifts the edge of the bar to be lifted above the drawing plane and makes it easy to push in and clamp the drawing sheet.

According to this invention, it is suggested to form the board with a sloped slot at a right angle to the clamping bar, so that the clamping bar, especially along the lower edge of the drawing sheet, is protected against nicking and tearing. Also, the position of the drawing is always located properly. The drawing sheet rests with one edge within the slot and is protected. Another aspect of the invention is the provision of a movable scale on the edge or within a groove of the clamping bar. The scale can be operated in conjunction with the measuring scale on the guide edge,

FIG. I shows that the drafting device has a flat board I formed with guide grooves 2 on its top face on all four sides spaced a certain distance from the edges. These guide grooves are going through the plate on one end in length direction, and the other end of the groove ends in such a distance from the neighboring plate edge that between the grooves 2, in a right angle to each other, a land 20 remains, which is the same as the thickness of the board. These distances 2c between the two guide grooves 2 meeting in a right angle give the board sufficient strength.

With the help of guide grooves 2, a straightedge 3 for drafting, having, for example, the shape of a triangle with unequal sides, is guided accurately by parallel displacement. To achieve this action, the guide grooves 2 in the board 1 are of trapezoidal-shaped cross section, as can be seen in FIG. 2. Every guide edge 2a of guide groove 2 close to the table edge, is directed vertical to the plate plane and the other guide edge 2b slopes upwardly to the drawing plane.

The straightedge 3 has on its underside at least one guide piece 4 for engaging the guide grooves 2 of plate I. The cross section of guide piece 4 is fitted to the cross section of the guide groove 2. The guide piece 4 has a support edge 4a vertical to its plane which is engaged with groove edge 2a and furthermore is equipped with a sloped guide edge 4b, which engages the groove edge 2b.

By gripping the board I with the inside of the left hand and at the same time engaging the left-hand thumb with a hole 5 in the straightedge 3, the latter will be pressed, with the edge 40 of guide piece 4, against the edge 2a of the guide groove 2 and by this action, the straightedge will be straightened out. Its drawing or measuring edge will be exactly at a right angle to its path on the drawing plane of the board. By longitudinal displacement of the straightedge 3 with its guide pieces 4 within guide groove 2 of plate 1, it is possible to draw any number of parallel lines on the drawing on plate 1. To make vertical lines at right angles to the parallel lines, it is only necessary to engage the straightedge 3 with its guide piece 4 in a guide groove 2 at a right angle to the first-used guide groove 2 and to achieve the same action with the drafting device turned 90. Because guide grooves are present on all four sides of the board, the drafting plane may be carried over quite close to the edges.

The exchange of the rest position of the straightedge 3 within the different guide grooves of plate I is made easier by the combined action of the sloped groove edges 2b with the sloped guide areas 4b which are present on the guide piece 4 arranged on the underside of the straightedge 3. For disengaging of guide piece 4 from the guide groove 2 being used, it is necessary to push with the thumb, engaged into hole 5 of straightedge 3, away from the plate edge towards the drawing plane, to slip the guide piece 4 from the used guide groove 2. A simple swinging of the straightedge around the thumb in the direction to the guide groove 2 to be used next, engaged in hole 5, will bring the straightedge into a position in which its guide piece 4 may be slipped easily into the next guide groove to be used. The swinging of the straightedge 3 on the board is easier when a turn piece 6 is inserted into hole 5; this turn piece 6 is equipped with radial grooves into which the thumb of the hand guiding the straightedge 3 may engage while turn It may also be of advantage to insert a permanent magnet 7 into the underside of the turn piece 6 when the recessed clamping bar 8 is made from magnetically attracted material. In this case, the straightedge will be maintained in a straight position automatically by the force of the permanent magnet 7 operating on the clamping bar 8. A magnetic strip 11 may be arranged within the recess 9, pulling the clamping bar 8 down by its magnetic force and keeping a drawing sheet in exact position. So that the drawing sheet may be inserted or taken out and the clamping bar 8 lifted against the action of the magnet strip 11, the edge of recess 9 is provided with at least one finger recess. This finger recess makes it possible to exert a pressure on the edge 8a of clamping bar 8 and with this pressure to tilt it. To make it possible for the clamping bar 8 to tilt into the recess 9, the recess has in its center a longitudinal projection 9a. The clamping bar 8 has, approximately in the center of its cross section, a U-shaped impression 13. The edge 13a of the impression l3 rests, by exerting pressure with the finger, with the length edge 8a of clamping bar 8 on the projection 9a of recess 9 and acts as tilt edge for clamping bar 8. The other edge 13b of the U-shaped impression 13 serves as a stop during the insertion of the drawing 10 under the edge of the clamping bar 8. On the clamping bar 8 a scale 14 may be movably arranged and kept in place by a magnetic strip 15. The scale 14 may also be movably arranged in one of the guide grooves 2 of board as shown in FIG. 2 on the right-hand edge. Also, on the left-hand side may be arranged a scale 14 in the same way as shown in FIG. 20.

So that an exact measuring of distances on each place of the drawing area is possible with the help of the straightedge 3 without hindrance by the guide piece 4, it is necessary to give the guide piece 4 a special shape. In the design of the straightedge 3 according to the FIGS. 31:, 3b, and 3c, the guide piece 4 has a constant thickness over the largest part of the straightedge up to an edge 4c positioned a distance from the measuring edge 30 and parallel to it. From this edge 40 on, the guide piece is sloped in the direction of measuring edge 3a. The edge 4c of the guide piece 4 then forms a tilt edge for the straightedge. Around this tilt edge the measuring edge may be brought to a tight fit at all positions of the drawing area, by a corresponding pressure with the finger, at a point between the measuring edge 30 and the tilt edge 4c.

In the design of the straightedge according to FIGS. 4a, 4b, and 4c, the guide piece 14 ends directly on the tilted edge 140, that is, a slope towards the measuring edge 13a is not present.

On the place of a guide piece which extends uninterrupted over the largest part in its width over the guide edge, it is also possible, as shown in FIGS. 5a, 5b, 50, 6a, 6b and 6c, 7a, 7b, and 7c, to use at least two section, of which one is such a distance from the measuring edge that this edge faces the measuring edge and serves as a tilting edge.

The design of the straightedge, in accordance with FIGS. 60, 6b, 6c and 7a, 7b, and 7c, differs from the design, according to the FIGS. 5a to 50 mainly in that the portions are not formed as pointed swellings, but as impressions. According to the design shown in FIGS. 7a and 7b, the humps are formed by a corrugated edge; in this arrangement, Ihumps are formed on the top and bottom surfaces of the straightedge. By this method, it is possible to used the straightedge easily in two planes from each other. The straightedge 53 as shown in FIGS. 8a and 8b is a variation of the form shown in FIGS. 3a and 3b insofar as the guide piece 54 has the shape of a wedge starting from the edge of the straightedge, opposite the measuring edge 53a, and close to the measuring edge 53a. In this design, the measuring edge 53a fits tightly on the drawing surface over its total length, without it being necessary to tilt the guide piece 54 around a tilt edge. The guide piece 54 according to FIG. 8b has on its thickest end, :i.e., the end directed away from the measuring edge 53a, a slope 54d which makes it easy to slide the straightedge 53 over the different grooves and recesses within the drawing board, when the guide piece of the straightedge is disengaged from the grooves, to execute certain drawing operation.

As can be seen from the FIGS. 9a and 9b, for achieving an accurate guide of the straight edge on the board 61, it is only necessary to form in the top of board 61, grooves having the shape of a wedge and position them a certain distance from each other. With these wedge-formed grooves is used a corresponding edge piece beveled with dull edges as a guide piece for the straightedge 63. This edge piece is arranged transversely to the measuring edge. The elasticity present within the guide edge 63 in the area of the dull beveled edges permits, by elastic pressure to the straightedge 63, the measuring edge to rest completely on the drawing area.

FIGS. 10 to 19 of the drawing show different cross-sectional shapes for the design of guide grooves within the board and also of the guide pieces on the straightedges. According to FIG. 10, the guide grooves 72 and the guide pieces 74 are of rectangular cross sections. In FIG. II, the grooves 82 and guide pieces 84 have the shape of a trapezoid.

According to FIG. 12 the cross section of the guide grooves 92 within the drawing board is of trapezoidal shape as in FIG. 11; however, the guide piece 94 is designed with a hump extending from the underside.

FIG. 13! shows the guide grooves 102 as having a triangular shape; however, the engaging guide piece 104 of straightedge 103 has the shape of a trapezoid.

The guide piece 114 on straightedge 113 is fitted to the trapezoid-shaped grooves 112 of FIG. 14 by fitting in a certain edge thickness. According to FIG. 15, a sloped edge on the side of the straightedge 123 engages the trapezoid-shaped guide groove 122 of the board, as a guide piece 124. FIGS. 16 and 16a show a design of the guide piece 134 on the straightedge 133, which permits a combined operation for adiustment with the circumferential edges of the board and also permits the interlock with guide grooves 132 of the board.

The FIG. 17 shows a design variation for the guide pieces M4 of straightedge 143, makes it possible to use both sides of the straightedge in cooperation with the guide grooves 142 of the board. FIG. 18 is similarly designed with a straightedge 153 having a guide piece 154 operating in a groove 152.

FIG. 19 shows that in addition to guide grooves 2 for the straightedge within the board 1, additional sloped slots 16 may be arranged into which the edge of the drawing sheet may be inserted, so that tearing of the sheet during drafting work is eliminated.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

We claim:

1. Drawing apparatus, comprising a. a board for holding a paper sheet, the board being formed with guide grooves parallel and adjacent to its outer edges,

b. a straightedge member movable on the board, the straightedge having a working edge and being formed with a guide piece positioned at a right angle to its working edge and slidable in a guide groove, so that the straightedge is movable in a direction parallel to the guide piece, the guide grooves and the guide piece having the shape of a trapezoid with the larger base at the open part of the groove and the smaller base forming the bottom of the groove, the guide piece terminating a substantial distance from the working edge of the straightedge, and the guide piece being formed as a short bar and terminating a substantial distance from the measuring edge of the straightedge member to form a tilt edge.

2. Drawing apparatus as recited in claim 1, wherein the guide piece of the straightedge member is formed like a wedge, its thickness increasing from the measuring edge.

3. Drawing apparatus as recited in claim 1, wherein the guide piece slopes from a tilt edge to the measuring edge of the straightedge.

4. Drawing apparatus as recited in claim 1, wherein the guide piece is formed in two discrete portions of which one is located a substantial distance from the measuring edge of the straightedge member and so forms a tilt edge.

5. Drawing apparatus as recited in claim 1, wherein the guide piece is formed as a corrugated strip along at least one side of the straightedge member.

6. Drawing apparatus as recited in claim 1, wherein the guide piece is equipped with a bevel at the end opposite the measuring edge.

7. Drawing apparatus as recited in claim 1, wherein the guide piece is beveled on the side closer to the adjacent parallel edge of the board.

8. Drawing apparatus as recited in claim 1, wherein a grip hole is arranged within the straightedge member close to the guide piece and to the measuring edge and wherein a turn piece is built into the grip hole.

9. Drawing apparatus as recited in claim 8, wherein the turn piece has radial grooves.

10. Drawing apparatus as recited in claim 8, wherein the turn piece of the straightedge member contains a magnet.

11. Drawing apparatus, comprising a. a board for holding a paper sheet, the board being formed with guide grooves parallel and adjacent to its outer edges,

b. a straightedge movable on the board, the straightedge having a working edge and being formed with a guide piece positioned at a right angle to its working edge and slidable in a guide groove, so that the straightedge is movable in a direction parallel to the guide piece, the guide grooves and the guide piece having the shape of a trapezoid with the larger base at the open part of the groove and the smaller base forming the bottom of the groove, the guide piece terminating a substantial distance from the working edge of the straightedge,

. a clamping bar recessed beneath the drawing plane in the board for locking the drawing paper in working position, and

d. a recess for receiving the clamping bar limited by barriers on all sides with said barriers positioned at the same height as the drawing plane.

12. Drawing apparatus as recited in claim 11, wherein extending from the recess for the clamping bar are depressions which are formed in the board for pressing the clamping bar into the drawing plane.

13. Drawing apparatus as recited in claim 11, wherein the clamping bar has a U-shaped impression approximately in the cross-sectional center which forms an alignment stop for the paper sheet.

14. Drawing apparatus as recited in claim 11, wherein on the base of the recess is located a ridge on which the clamping bar is supported.

15. Drawing apparatus as recited in claim 11, wherein at a right angle to the clamping bar is formed a sloped slot as an inlet for the drawing paper.

16. Drawing apparatus as recited in claim 11, wherein a scale is provided on the clamping bar.

17. Drawing apparatus as recited in claim 16, wherein the scale is maintained in place by magnets on the clamping bar.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 539 16 Dated June 29 1971 Inventm-(s) Walter Hebel et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet insert:

-- Foreign Application Priority Data June 18, 1968 Germany P17 61 622.7

Signed and sealed this 20th day of August 1974.

(SEAL) Attest:

MCCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) USCOMM DC omnmpuo 

1. Drawing apparatus, comprising a. a board for holding a paper sheet, the board being formed with guide grooves parallel and adjacent to its outer edges, b. a straightedge member movable on the board, the straightedge having a working edge and being formed with a Guide piece positioned at a right angle to its working edge and slidable in a guide groove, so that the straightedge is movable in a direction parallel to the guide piece, the guide grooves and the guide piece having the shape of a trapezoid with the larger base at the open part of the groove and the smaller base forming the bottom of the groove, the guide piece terminating a substantial distance from the working edge of the straightedge, and the guide piece being formed as a short bar and terminating a substantial distance from the measuring edge of the straightedge member to form a tilt edge.
 2. Drawing apparatus as recited in claim 1, wherein the guide piece of the straightedge member is formed like a wedge, its thickness increasing from the measuring edge.
 3. Drawing apparatus as recited in claim 1, wherein the guide piece slopes from a tilt edge to the measuring edge of the straightedge.
 4. Drawing apparatus as recited in claim 1, wherein the guide piece is formed in two discrete portions of which one is located a substantial distance from the measuring edge of the straightedge member and so forms a tilt edge.
 5. Drawing apparatus as recited in claim 1, wherein the guide piece is formed as a corrugated strip along at least one side of the straightedge member.
 6. Drawing apparatus as recited in claim 1, wherein the guide piece is equipped with a bevel at the end opposite the measuring edge.
 7. Drawing apparatus as recited in claim 1, wherein the guide piece is beveled on the side closer to the adjacent parallel edge of the board.
 8. Drawing apparatus as recited in claim 1, wherein a grip hole is arranged within the straightedge member close to the guide piece and to the measuring edge and wherein a turn piece is built into the grip hole.
 9. Drawing apparatus as recited in claim 8, wherein the turn piece has radial grooves.
 10. Drawing apparatus as recited in claim 8, wherein the turn piece of the straightedge member contains a magnet.
 11. Drawing apparatus, comprising a. a board for holding a paper sheet, the board being formed with guide grooves parallel and adjacent to its outer edges, b. a straightedge movable on the board, the straightedge having a working edge and being formed with a guide piece positioned at a right angle to its working edge and slidable in a guide groove, so that the straightedge is movable in a direction parallel to the guide piece, the guide grooves and the guide piece having the shape of a trapezoid with the larger base at the open part of the groove and the smaller base forming the bottom of the groove, the guide piece terminating a substantial distance from the working edge of the straightedge, c. a clamping bar recessed beneath the drawing plane in the board for locking the drawing paper in working position, and d. a recess for receiving the clamping bar limited by barriers on all sides with said barriers positioned at the same height as the drawing plane.
 12. Drawing apparatus as recited in claim 11, wherein extending from the recess for the clamping bar are depressions which are formed in the board for pressing the clamping bar into the drawing plane.
 13. Drawing apparatus as recited in claim 11, wherein the clamping bar has a U-shaped impression approximately in the cross-sectional center which forms an alignment stop for the paper sheet.
 14. Drawing apparatus as recited in claim 11, wherein on the base of the recess is located a ridge on which the clamping bar is supported.
 15. Drawing apparatus as recited in claim 11, wherein at a right angle to the clamping bar is formed a sloped slot as an inlet for the drawing paper.
 16. Drawing apparatus as recited in claim 11, wherein a scale is provided on the clamping bar.
 17. Drawing apparatus as recited in claim 16, wherein the scale is maintained in place by magnets on the clamping bar. 